Long-lasting drug-associated memories can contribute to relapse; therefore these memories must be inactivated to enable sustainable success in addiction therapy. As drug associations are usually acquired over several conditioning events, we assume that an effective treatment should be repeatedly applied to achieve persistent effects. In this study, we examine whether 10 repeated memory reactivation tests followed by systemic N-methyl-D-aspartate receptor antagonist MK-801 (0.1 mg/kg) administrations can disrupt memory reconsolidation in rats, leading to a reduction of well-established amphetamine-conditioned place preference (CPP). We found that immediate (but not 60-min delayed) administration of MK-801 after the tests reduced amphetamine-CPP expression after at least four treatments. These effects were specific to CPP expression as no MK-801-induced change in locomotion was observed during all tests. We discuss these results as being caused by MK-801 disrupting memory reconsolidation and we propose the applied repeated-treatment regimen as a new therapeutic research strategy to persistently disrupt drug-associated memories.
Neuropharmacology, Zoological Institute, Faculty of Biology, University of Tübingen, Tübingen, Germany
Correspondence to Dr Volker Herzig, Neuropharmacology, Zoological Institute, Faculty of Biology, University of Tübingen, Auf der Morgenstelle 28 E, 72076 Tübingen, Germany
†Werner J. Schmidt deceased.
Received 4 February 2007 Accepted as revised 11 July 2007